Multi-node data synchronous acquisition system and method for real-time monitoring of underwater surface deformation

ABSTRACT

A multi-node data synchronous acquisition system and a method for real-time monitoring of underwater surface deformation. The system includes at least four sensor arrays, where each of the sensor array consists of a plurality of ribbon-like rigid substrates connected by movable joints. On each section of rigid substrate, three sensor units are respectively connected to a slave station data acquisition unit through cables. The slave station data acquisition unit is connected with a central controller through a cable. The central controller includes a compressive cabin outside and an embedded controller and a power supply inside. Each slave station data acquisition unit acquires data from an MEMS attitude sensor and then transmits it to the embedded controller. The present invention may realize synchronous acquisition of underwater or even underwater multi-node data, implement three-dimensional surface reconstruction, and may be used for improving the ocean observation capability.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from Chinese PatentApplication No. CN 201810373718.3, filed on Apr. 24, 2018. The contentof the aforementioned application, including any intervening amendmentsthereto, is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to the technical field of oceanobservation, and more particularly to a multi-node data synchronousacquisition system and a method for real-time monitoring of underwatersurface deformation.

BACKGROUND OF THE INVENTION

There are abundant mineral resources in the ocean covering about 75percent of the Earth's surface. Many technical equipment and projects ofbuilding ports, laying underwater pipelines and measuring channels areneeded in an ocean exploration and development process. In the 21stcentury, the economic development of various countries in the world isinseparable with the vast ocean. In particular, with the rapiddevelopment of the economy and the explosion of the population, thedemand for energy increases rapidly, people set their sights on theocean, especially the deep sea, to survey, develop and utilize the oceanresources. China is a country having a sea area covering nearly 3million square kilometers, so it is significant to develop and researchthe ocean. Underwater monitoring becomes a vital part of the research onocean and underwater engineering construction. At present, relevanttechniques in a ground surface monitoring project are relatively mature.The intelligent monitoring technique is booming, and an observationsystem is perfectly developed. However, the underwater curved surfacemonitoring is poor in research foundation. As China vigorously developsthe marine industry, the underwater surface monitoring is applied inmore fields. For underwater topography monitoring, such as explorationand trial production of underwater natural gas hydrates, the natural gashydrates are extremely fragile on the seabed as their structuralstability is susceptible to changes in temperature and pressure. Thiswill cause large-scale changes in underwater topography, and destroyunderwater engineering facilities such as deep-sea oil pipelines andunderwater monitoring. Accordingly, it is important and urgent tomonitor the underwater surface deformation.

Time synchronization may be a challenge for data acquisition in the deepsea, especially on the seabed. The time synchronization is one of thekey techniques of an underwater sensor network. It is meaningful tomatch data acquired by distributed sensor nodes with time information,which is the basis for achieving techniques of network collaborativework, collaborative sleep and the like. Currently, the technique of thetime synchronization of systems on land is relatively mature. However,the environment in the ocean is more complex. The most common way is touse the time synchronization technique of a GPS-based distributed dataacquisition system on land, but seawater may shield transmission ofelectromagnetic waves, light waves, and other signals. Accordingly, itis impossible to use, in a deep-sea environment, an independenthigh-precision clock reference source such as a GPS or a Beidou timescaler universal on land. In this way, it is very important to know howto realize multi-node and long-term synchronous acquisition of deep-seasensing data. Meanwhile, this method may be effectively applied to acase where the universal, independent and high-precision clock referencesource may be unavailable, which has a good expandability.

The Chinese Patent Application No. CN105674945A discloses a underwaterlandslide monitoring apparatus based on an MEMS sensor and a monitoringmethod thereof. A monitoring unit consists of a plurality of monitoringsubunits connected in series. The monitoring unit is disposed in aprotective cover. The monitoring unit transmits a monitored signal to aprocessing unit. The processing unit transmits the processed signal to acomputer terminal. The MEMS sensor is fixed in a long tube, and one endof the long tube is connected with one end of a flexible connectiontube. The MEMS sensor is connected with a data input port of a dataprocessor. The data processor transmits the processed data to thecomputer terminal. However, on the one hand, an array structure of thepresent invention is of a circular tube shape. It is necessary toprevent the array structure from being twisted in a deployment process.The longer the distance is, the greater the probability of deformationis. The deployment difficulty is greatly increased. On the other hand,the sensor in the array is an acceleration sensor. The series deploymentis only capable of monitoring two-dimensional deformation rather thaneffectively monitoring three-dimensional deformation in a monitoringarea, so data synchronous acquisition cannot be ensured.

The Chinese Patent Application No. CN107339969A discloses an underwatersurface deformation monitoring system based on an MEMS attitude sensor,including a computer, an underwater data storage unit and a plurality ofparallel ribbon-like sensor arrays. The computer is connected with eachsensor array through the underwater data storage unit. Each sensor arrayis sealed from outside by a packaging material, and includes multiplesections of rectangular tubes connected by flexible joints inside. OneMEMS attitude sensor is arranged in each section of rectangular tube.Each MEMS attitude sensor is connected with an acquisition unit througha cable. The acquisition unit is connected with an underwater mastercontrol unit. The MEMS attitude sensor is a 9-axis attitude sensorincluding a three-axis accelerometer, a three-axis gyroscope and athree-axis magnetometer, which is capable of fusing obtainedacceleration data, angular velocity data and magnetic field strengthdata to obtain attitude information and displaying them in a data formof an Euler angle or quaternion. However, the underwater surfacedeformation monitoring system of the present invention is incapable ofguaranteeing data synchronous acquisition, so that the subsequentthree-dimensional reconstruction precision is poor. Moreover, eachsensor array is poor in reliability due to the stainless steelrectangular tubes and the rubber flexible joints, and has a probabilityof deformation because the joints are easily damaged. The 9-axisattitude sensor serves as the MEMS attitude sensor, which is high inenergy consumption and is not suitable for long-term underwaterdeployment.

SUMMARY OF THE INVENTION

A technical problem to be solved by the present invention is to overcomethe deficiencies in the prior art and provide a multi-node datasynchronous acquisition system and a method for real-time monitoring ofunderwater surface deformation.

In order to solve the technical problem, the present invention has thefollowing solution.

There is provided a multi-node data synchronous acquisition system forreal-time monitoring of underwater surface deformation, including acentral controller and sensor arrays provided with MEMS attitudesensors. The system includes at least four sensor arrays, and each ofthe four sensor arrays consists of a plurality of sections ofribbon-like rigid substrates connected by movable joints. Three sensorunits and one slave station data acquisition unit are arranged on eachsection of rigid substrate. The sensor unit includes a compressive cabinoutside and an MEMS attitude sensor and a power supply inside. Eachslave station data acquisition unit includes a compressive cabin outsideand a slave station data acquisition unit control board and the powersupply inside. The three sensor units are respectively connected to theslave station data acquisition unit through cables. The slave stationdata acquisition unit is connected to a central controller through thecable. The central controller includes a compressive cabin outside andan embedded controller and the power supply inside. The slave stationdata acquisition unit acquires data from the MEMS attitude sensors andthen transmits it to the embedded controller.

In the present invention, the slave station data acquisition units areconnected with the sensor units and the central controller throughwaterproof connectors and cables, respectively.

In the present invention, the MEMS attitude sensor is a 3-axisacceleration sensor capable of fusing obtained acceleration data toobtain attitude information and displaying it in a data form of aquaternion or Euler angle.

In the present invention, a clamp for radial surrounding is disposedoutside the compressive cabin of the sensor unit, and the sensor unit ismounted on a mounting position of the rigid substrate by the clamp.

In the present invention, the compressive cabin of the centralcontroller is provided with a spike fixing member for fixation at thelower end and an (elliptical) annular suspension hook at the upper end.

In the present invention, the rigid substrates are stainless steelplates. The movable joint connecting adjacent rigid substrates is astainless steel movable hinge. A rotary suspension ring for connectingan underwater mechanical arm is arranged at a head end of each sensorarray. The power supply includes a 5V mobile power supply and a 24Vlithium battery pack. The former supplies power to the slave stationdata acquisition unit, and the latter is formed by series or parallelconnection of lithium batteries to supply power for each centralcontroller. A data transmission is realized between the sensor units andthe slave station data acquisition unit through analog IIC buses. Thedata transmission is realized between the slave station data acquisitionunit and the central controllers through CAN buses. Synchronous timesignals are transmitted and issued by an I/O port.

The present invention further provides a multi-node data synchronousacquisition method for real-time monitoring of underwater surfacedeformation using the foregoing system, including:

(1) building a synchronous acquisition system, assembling thesynchronous acquisition system, where each central controller isprovided with at least 4 sensor arrays; a circuit connectionrelationship between the central controllers and the slave station dataacquisition units as well as the sensor units is as follows: every threesensor units as a group are connected to one slave station dataacquisition unit, and independently transmit data through three analogIIC buses, each of the analog IIC buses includes an SDA cable and an SCLcable, and the SDA and the SCL are respectively connected to a VCCinterface of the acquisition unit through pull-up resistors, each slavestation data acquisition unit transmits data to the central controllerthrough a common CAN bus, the CAN bus includes a CAN_H, a CAN_L and two120Ω terminal resistors, and a CAN controller determines a bus levelbased on a potential difference between the CAN_H cable and the CAN_Lcable (the bus level includes a dominant level and a recessive level, itis one or the other, and a transmitter transmits a message to a receiverby changing the bus level);

(2) lowing the synchronous acquisition system to the seabed by anunderwater winch, and mounting it by utilizing an underwater robot, sothat the spike fixing member at the lower end of the central controlleris inserted into a underwater formation for fixation, and grasping arotary suspension ring at the head end of each sensor array by theunderwater robot to drag each sensor array to be evenly arranged on theseabed in a radial direction using the central controller as a center(for example, four sensor array are crossed);

(3) taking a clock of the central controller as a master clock of thesystem, sequentially transmitting calibration time point information toeach slave station data acquisition unit through a CAN bus in advance,simultaneously issuing time signals by an I/O port, and simultaneouslycalibrating respective time by the slave station data acquisition unitafter receiving the time signals to achieve relative synchronization ofthe clock of the data acquisition system; and

(4) after the sensor units acquire acceleration data of each physicalpoint, transmitting the data to the adjacent slave station dataacquisition unit through an analog IIC bus, time-stamping the data bythe slave station data acquisition unit after classifying and numbering,then transmitting the data to the CAN bus, and summarizing the data ofthe slave station data acquisition units by the central controllerthrough the CAN bus to complete storage and preprocessing of the data.

Principles

In the technical solution of the present invention, the sensor arrays ofthe sensor nodes are carriers for providing mounting spaces for theslave station data acquisition units and the MEMS accelerometeracquisition nodes, and are composed of a plurality of sections ofribbon-like rigid substrates and intermediate movable joints. The MEMSaccelerometer sensors and the compressive cabins of the slave stationdata acquisition units are arranged on respective sections ofribbon-like rigid substrates. Each section is 50 cm in length, and thesections are connected by the movable joints. The MEMS accelerometeracquisition nodes acquire acceleration data of each physical point forreconstruction of the subsequent three-dimensional underwatertopography. The slave station data acquisition units are arranged withinthe compressive cabins, and acquire the data of the three adjacent MEMSacceleration sensor acquisition nodes through analog IIC buses. Eachdatum is time-stamped at the end, and the acquired data is transmittedto the CAN buses, so that transfer and long-distance transmission of thedata are realized. The central controller is also arranged within thecompressive cabin, and as a main clock, issues a regular timeinstruction through an I/O port to realize relative time synchronizationof the system, and acceleration data in the slave station dataacquisition units is summarized through the CAN buses to completestorage and pre-processing of the data.

The sensor arrays of the sensor nodes are lowered to the seabed by theunderwater winch, the rotary suspension ring at the head end of eachsensor array is grabbed by a ROV to drag and pull the sensor arraycoiled in a winch turntable, and the four sensor arrays are placed onthe seabed in a cross shape using the underwater winch as a center. Thecentral controller is placed on the seabed by a rope, and then installedby the ROV, so that a spike fixing member at the lower end thereof isinserted into a seabed formation for fixing the compressive cabin. TheMEMS accelerometer acquisition nodes may acquire the acceleration dataof each physical point, and then transmit the data to the adjacent slavestation data acquisition units through the analog IIC buses. After theslave station data acquisition unit classifies and numbers the data, ittime-stamps the data and then transmits the time-stamped data to the CANbus. The central controller summarizes the data of each slave stationdata acquisition unit through the CAN bus, and completes storage andpre-processing of the data. Moreover, the central controllersequentially transmits calibration time point information to each slavestation data acquisition unit through the CAN bus, and then periodicallycalibrates the time of the slave station data acquisition unit using theI/O port to achieve relative data synchronous acquisition of the system.

Preferably, the compressive cabin of the central controller and thecompressive cabins of the slave station data acquisition units arecylindrical cabins, with the advantages of being easy to manufacture,high in utilization rate of internal spaces and small in fluid movementresistance. Each compressive cabin is made of stainless steel, which isgood in comprehensive performance, resistant to high pressure andcorrosion and easy to machine. Each compressive cabin is internallyprovided with components such as a main control board, a storage moduleand a power supply. It is necessary to replace the power supply andextract the stored data in a use process, so that a reliable static sealis required between the compressive cabin and an upper end cover. Thepresent invention adopts a rubber O-shaped ring sealing method. O-shapedrings are mounted within corresponding closed sealing grooves to ensurethat no leakage is caused during underwater operation. More preferably,the O-shaped rings are selected from two specifications with wirediameters of 10 mm and 5.7 m, respectively, and the inner diameters ofthe O-shaped rings are determined according to radial dimensions of thecompressive cabins.

The MEMS accelerometer acquisition nodes are configured to acquireacceleration data of each physical point for subsequentthree-dimensional surface reconstruction. As an application example, theMEMS accelerometer acquisition nodes may employ ADXL335. The maincontrol boards of the slave station data acquisition units areconfigured to classify and number the acceleration data and time-stampit. As an application example, control units of the main control boardsof the slave station data acquisition units may employ STM32F103ZET6.The control board of the central controller is configured to summarizethe data of each slave station data acquisition unit, complete storageand pre-processing of the data, and transmit the calibration time pointinformation in advance and periodically transmit a time instruction toachieve relative data synchronous acquisition of the system. As anapplication example, the control board of the central controller mayemploy a CX5100 of BECKHOFF. The storage module is configured to storedata obtained from the MEMS acceleration sensor acquisition nodes. As anapplication example, the storage module may employ a Micro SD cardread-write module and a 32 GB Micro SD card of BECKHOFF. A power moduleis configured to supply voltages of respectively 24V and 5V to thecentral controller and the slave station data acquisition units, whereinthe voltage 24V is provided by lithium batteries in series or inparallel. As an application example, the 5V lithium batteries of theSCUD may be employed.

Compared with the prior art, the present invention has the followingbeneficial effects.

(1) The multi-node data synchronous acquisition system for real-timemonitoring of underwater surface deformation of the present inventionmay realize synchronous acquisition of underwater or even underwatermulti-node data, implement three-dimensional surface reconstruction, andmay be used for improving the ocean observation capability.

(2) The present invention innovatively proposes a manner of matching theIIC buses with the CAN buses to realize long-distance transmission ofthe data, utilizes the clock of the master station as the clock sourceof the system and adopts a manner of issuing the time instructions bythe I/O port on time to implement the time synchronization within thesystem, and may effectively solve the problem of time synchronization ofthe system in which the independent high-precision clock such as the GPSor Beidou time scaler universal on land may not be used as a referencesource.

(3) In the present invention, the ribbon-like rigid substrates on whichthe sensor arrays of the sensor nodes are mounted are made of stainlesssteel plates, the movable joints among the sections are stainless steelmovable hinges, the rotary suspension ring is arranged at the head endof each sensor array at which the sensor nodes are mounted, and thesensor array is further provided with a hoop, so that the system maywork stably and reliably, and is greatly convenient to mount and deployunderwater.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an overall external structure ofthe present invention;

FIG. 2 is a partial schematic diagram of a sensor array of an MEMSsensor node of the present invention;

FIG. 3 is a schematic diagram of a central controller of the presentinvention;

FIG. 4 is a schematic diagram showing the installation of a sealinghousing of the present invention; and

FIG. 5 is a schematic diagram showing the structures of a ribbon-likerigid substrate and an intermediate movable joint of the presentinvention.

Reference numerals in accompanying drawings: 1—rotary suspension ring;2—clamp; 3—sensor unit; 4—four-core waterproof connector; 5—eight-corewaterproof connector; 6—movable joint; 7—rigid substrate; 8—slavestation data acquisition unit; 9—four-core waterproof connector;10—central controller; 11—sensor array; 12—power supply; 13—MEMSattitude sensor; 14—power supply; 15—slave station data acquisition unitcontrol board; 16—annular suspension hook; 17—power supply; 18—centralcontroller control board; and 19—spike fixing member.

DETAILED DESCRIPTION OF EMBODIMENTS

A multi-node data synchronous acquisition system for real-timemonitoring of underwater surface deformation will be further describedin detail below with reference to accompanying drawings and specificimplementations.

As shown in FIG. 1 to FIG. 4, the multi-node data synchronousacquisition system for real-time monitoring of underwater surfacedeformation includes four sensor array 11 with rotary suspension rings 1at head ends for connecting an underwater mechanical arm for deployment.Sensor units 3 and slave station data acquisition units 8 arerespectively mounted on the sensor array by clamps 2. The sensor units 3are internally provided with MEMS attitude sensors 13 (for example,3-axis acceleration sensors) and 3.3V power supplies 12 for acquiringacceleration information of physical points where they are located.Four-core waterproof connectors 4 are mounted on upper end covers of thesensor units 3, and connected onto the adjacent slave station dataacquisition units 8 through cables. The slave station data acquisitionunits 8 are internally provided with slave station data acquisition unitcontrol boards 15 and 5V power supplies 14, and are responsible foracquiring data of acquisition nodes of the adjacent three sensor units 3through analog IIC buses. Each datum is time-stamped at the end, and theacquired data is transmitted to CAN buses. Four-core waterproofconnectors 4 and eight-core waterproof connectors 5 are respectivelyarranged at upper and lower end covers of each slave station dataacquisition unit 8. The four sensor arrays 11 are arranged in a crossshape, and connected to the central controller 10 through cables in themiddle. The data of each slave station data acquisition unit issummarized through the CAN bus to complete storage and pre-processing ofthe data. Calibration time point information is transmitted to eachslave station data acquisition unit in advance through the CAN bus, andthen the time of the slave station data acquisition unit is periodicallycalibrated by adopting the I/O port to achieve relative data synchronousacquisition of the system. The central controller 10 is internallyprovided with a central controller control board 18 and a 24V powersupply 17. An upper end cover is provided with an elliptical suspensionring 16 for connection with the underwater mechanical arm duringlowering. A lower end cover is provided with a spike fixing member 19 ofa compressive cabin of the central controller for insertion into aseabed formation for fixing the compressive cabin.

As shown in FIG. 5, ribbon-like rigid substrates 7 and a movable joint 6constitute a flexible sensor array. When the sensor array is deployed ina horizontal plane, an angle between the ribbon-like rigid substrates 7is 0 degree. When changes in a surface, the angle between theribbon-like rigid substrates 7 is changed by rotating the movable joint6. Accordingly, this structure may greatly reduce the probability ofdeformation.

The present invention has the following working procedure:

(1) building a synchronous acquisition system,

assembling the synchronous acquisition system, wherein each centralcontroller 10 is provided with at least 4 sensor array 11, a circuitconnection relationship between the central controllers 10 and slavestation data acquisition units 8 as well as sensor units 3 is asfollows: every three sensor units 3 as a group are connected to oneslave station data acquisition unit 8, and independently transmit datathrough three analog IIC buses, each of the analog IIC buses includes anSDA cable and an SCL cable, and the SDA cable and the SCL cable arerespectively connected to a VCC interface of the acquisition unit 8through pull-up resistors, each slave station data acquisition unit 8transmits data to the central controller 10 through a common CAN bus,the CAN bus includes a CAN_H, a CAN_L and two 120Ω terminal resistors,and a CAN controller determines a bus level based on a potentialdifference between the two cables CAN_H and CAN_L;

(2) lowing the synchronous acquisition system to the seabed by anunderwater winch, and mounting it by utilizing an underwater robot, sothat the spike fixing member at the lower end of the central controller10 is inserted into a underwater formation for fixation, and grasping arotary suspension ring 1 at the head end of each sensor array 11 by theunderwater robot to drag each sensor array 11 to be evenly arranged onthe seabed in a radial direction using the central controller 10 as acenter;

(3) taking a clock of the central controller 10 as a master clock of thesystem, sequentially transmitting calibration time point information toeach slave station data acquisition unit 8 through a CAN bus in advance,simultaneously issuing time signals by I/O port, and simultaneouslycalibrating respective time by the slave station data acquisition unit 8after receiving the time signals to achieve relative clocksynchronization of the data acquisition system;

(4) after the sensor units 3 acquire acceleration data of each physicalpoint, transmitting the data to the adjacent slave station dataacquisition unit 8 through an analog IIC bus, time-stamping the data bythe slave station data acquisition unit 8 after classifying andnumbering it, then transmitting the data to the CAN bus, and summarizingthe data of the slave station data acquisition units by the centralcontroller 10 through the CAN bus to complete storage and preprocessingof the data.

It should be noted that the above description is only preferredembodiments of the present invention, and not intended to limit thepresent invention. Any modifications, equivalent substitutions,improvements, and the like, which are made within the spirit andprinciples of the present invention, should fall in the scope ofprotection of the present invention.

What is claimed is:
 1. A multi-node data synchronous acquisition systemfor real-time monitoring of underwater surface deformation, comprising:a central controller, and sensor array provided with MEMS attitudesensors; wherein the system comprises at least four sensor arrays, eachof the sensor arrays consists of a plurality of sections of ribbon-likerigid substrates connected by movable joints, three sensor units and oneslave station data acquisition unit are arranged on each section ofrigid substrate; each sensor unit comprises a compressive cabin outsideand an MEMS attitude sensor and a power supply inside, and each slavestation data acquisition unit comprises a compressive cabin outside anda slave station data acquisition unit control board and a power supplyinside; the three sensor units are respectively connected to the slavestation data acquisition unit through cables, and the slave station dataacquisition unit is connected to the central controller through a cable;each central controller comprises a compressive cabin outside and anembedded controller and a power supply inside; and each slave stationdata acquisition unit acquires data from the MEMS attitude sensors andthen transmits it to the embedded controller.
 2. The system according toclaim 1, wherein the slave station data acquisition units are connectedwith the sensor units and the central controllers through waterproofconnectors and cables, respectively.
 3. The system according to claim 1,wherein the MEMS attitude sensors are 3-axis acceleration sensorscapable of fusing obtained acceleration data to obtain attitudeinformation and displaying it in a data form of a quaternion or Eulerangle.
 4. The system according to claim 1, wherein a radial surroundingclamp is disposed outside the compressive cabin of each sensor unit, andeach sensor unit is mounted on a mounting position of each rigidsubstrate by the clamp.
 5. The system according to claim 1, wherein thecompressive cabin of the central controller is provided with a spikefixing member for fixation at the lower end and an annular suspensionhook at the upper end.
 6. The system according to claim 1, wherein therigid substrates are stainless steel plates, the movable jointconnecting adjacent rigid substrates is a stainless steel movable hinge,a rotary suspension ring for connecting an underwater mechanical arm isarranged at a head end of each sensor array, the power supply comprisesa 5V mobile power supply and a 24V lithium battery pack, wherein the 5Vmobile power supply supplies power to the slave station data acquisitionunit, and the 24V lithium battery pack is formed by series or parallelconnection of lithium batteries to supply power to each centralcontroller, the sensor units and the slave station data acquisitionunits realize data transmission through analog IIC buses, the slavestation data acquisition units and the central controllers realize datatransmission through CAN buses, and synchronous time signals aretransmitted and issued by I/O port.
 7. A multi-node data synchronousacquisition method for real-time monitoring of underwater surfacedeformation using the system according to claim 1, comprising: (1)building a synchronous acquisition system, assembling the synchronousacquisition system, wherein each central controller is provided with atleast four sensor arrays, a circuit connection relationship between thecentral controllers and slave station data acquisition units as well assensor units is as follows: every three sensor units as a group areconnected to one slave station data acquisition unit, and independentlytransmit data through three analog IIC buses, each of the analog IICbuses comprises an SDA cable and an SCL cable, and the SDA cable and theSCL cable are respectively connected to a VCC interface of theacquisition unit through pull-up resistors, each slave station dataacquisition unit transmits data to the central controller through acommon CAN bus, the CAN bus comprises a CAN_H, a CAN_L and two 120Ωterminal resistors, and a CAN controller determines a bus level based ona potential difference between the two cables CAN_H and CAN_L; (2)lowing the synchronous acquisition system to the seabed by an underwaterwinch, and mounting it by utilizing an underwater robot, so that thespike fixing member at the lower end of the central controller isinserted into a underwater formation for fixation, and grasping a rotarysuspension ring at the head end of each sensor array by the underwaterrobot to drag each sensor array to be evenly arranged on the seabed in aradial direction using the central controller as a center; (3) taking aclock of the central controller as a master clock of the system,sequentially transmitting calibration time point information to eachslave station data acquisition unit through a CAN bus in advance,simultaneously issuing time signals by I/O, and simultaneouslycalibrating respective time by the slave station data acquisition unitafter receiving the time signals to achieve relative clocksynchronization of the data acquisition system; and (4) after the sensorunits acquire acceleration data of each physical point, transmitting thedata to the adjacent slave station data acquisition unit through ananalog IIC bus, time-stamping the data by the slave station dataacquisition unit after classifying and numbering it, then transmittingthe data to the CAN bus, and summarizing the data of the slave stationdata acquisition units by the central controller through the CAN bus tocomplete storage and preprocessing of the data.